fix(starlark): use correct 'fileName' field from manifest (camelCase)

The Tronbyte manifest uses 'fileName' (camelCase), not 'filename' (lowercase).
This caused the download to fall back to {app_id}.star which doesn't exist
for apps like analogclock (which has analog_clock.star).

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

web_interface/blueprints/api_v3.py

@@ -7565,7 +7565,8 @@ def install_from_tronbyte_repository():
 
         try:
             # Pass filename from metadata (e.g., "analog_clock.star" for analogclock app)
-            filename = metadata.get('filename') if metadata else None
+            # Note: manifest uses 'fileName' (camelCase), not 'filename'
+            filename = metadata.get('fileName') if metadata else None
             success, error = repo.download_star_file(data['app_id'], Path(temp_path), filename=filename)
             if not success:
                 return jsonify({'status': 'error', 'message': f'Failed to download app: {error}'}), 500